focus.one-time unexpected behaviour

[RomkeVdMeulen]

I'm submitting a bug report

• Library Version:
  1.2.0

Please tell us about your environment:

• Operating System:
  Linux (Ubuntu)

• Node Version:
  6.9.4

• NPM Version:
  3.10.10

• JSPM
  JSPM 0.16.48

• Browser:
  Chrome 55

• Language:
  TypeScript 2.1.4

Current behavior:
If I want an element focused on render, but I'm not interested in keeping track of its focus state after that, I might do something like this:

<button focus.one-time="true">My Button</button>

In this case, attaching event listeners to the element only results in needless overhead.

Expected/desired behavior:
The Focus custom attribute should check if the binding mode is two-way and if not, should not attach event listeners to the element.

[RomkeVdMeulen]

While we're on the subject: I would expect the default binding mode of focus to be one-way. I usually bind it to an expression that cannot be assigned to:

  <a href="#" focus.bind="item === defaultItem">${item.name}</a>

If focus changes and comes back to this link, I'll get an error:

Uncaught Error: Binding expression "item === defaultItem" cannot be assigned to.

I can't speak for other developers, but I expect the most common use-case for the focus attribute to set initial focus, not to keep a property updated on whether an item is focused or not.

[Alexander-Taran]

attach focus from dialog is what you want..
https://github.com/aurelia/dialog/blob/master/src/attach-focus.ts
question is how many developers thought about using focus.one-way